Electrochemical biosensor and method for producing the same

ABSTRACT

An electrochemical biosensor includes a substrate, a plurality of layered active metal parts, a plurality of layered electrodes, a reaction confinement layer, an electrochemical reactive layer and a cover piece. The substrate is formed with through holes each of which is defined by an interior wall surface and penetrates top and bottom surfaces. Each of the layered active metal parts is formed at least upon a respective one of the interior wall surfaces. The layered electrodes are formed on the layered active metal parts. The reaction confinement layer confines a reactor space over a region where the through holes are formed. The electrochemical reactive layer is disposed in the reactor space and is electrically coupled to the layered electrodes.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.14/580,799, filed Dec. 23, 2014, which claims priority of TaiwanesePatent Application No. 102148419, filed on Dec. 26, 2013. Thisapplication claims the benefits and priority of all these priorapplications and incorporates by reference the contents of these priorapplications in their entirety.

FIELD OF INVENTION

Embodiments of the invention generally relates to biosensors and methodsfor producing the same, and more particularly to electrochemicalbiosensors and methods for producing the same.

BACKGROUND

Referring to FIG. 1, an electrochemical biosensor 8 is adapted formeasuring concentration of an analyte in a sample liquid, such as bloodsugar concentration in a blood sample, or the concentration of heavymeal pollutants in a wastewater sample. As shown in FIG. 1, theelectrochemical biosensor 8 includes an insulating substrate 81, ametallic conductive layer 82 formed on the insulating substrate 81 byprinting, an insulating layer 83 disposed to partially expose themetallic conductive layer 82, a reagent-reactive layer 84 in electricalcontact with the metallic conductive layer 82, and a cover plate 85.Although the electrochemical biosensor 8 may achieve the primary goal ofmeasuring the analyte concentration in the sample liquid, the metallicconductive layer 82, which is formed by screen printing, may exhibitrelatively high electrode impedance which results in attenuation andinterference of electrical output signals. In addition, the metallicconductive layer 82 of the electrochemical biosensor 8 may consume arelatively large amount of metallic raw material which increases theproduction cost.

Referring to FIG. 2, another electrochemical biosensor 9 is shown toinclude an insulating substrate 91, a pair of electrodes 92, anelectrochemical reactive layer 93 and a cover plate 94. The insulatingsubstrate 9 is formed with a reaction chamber 911 and a pair of throughholes 912 in spatial communication with the reaction chamber 911. Theelectrodes 92 are respectively disposed in the through holes 912, andthe electrochemical reactive layer 93 is disposed in the reactionchamber 911 to be electrically coupled with the electrodes 92. The coverplate 94 is disposed to cover the reaction chamber 911. Although theelectrochemical biosensor 9 may also achieve the primary function ofmeasuring the analyte concentration in the sample liquid, the electrodes92 and the substrate 91 are separately made, and a relativelycomplicated assembling procedure is therefore required. In addition,such configuration of the electrochemical biosensor 9 requiresrelatively low tolerance in making the electrodes 92 and the throughholes 911 and thereby increases the production cost.

SUMMARY

Certain embodiments of the present invention provide electrochemicalbiosensors that may alleviate the aforementioned drawbacks, and/ormethods for producing the same.

According to an aspect of the present invention, an electrochemicalbiosensor may include a substrate, a plurality of layered active metalparts, a plurality of layered electrodes, a reaction confinement layer,an electrochemical reactive layer and a cover piece.

The substrate is made of an electrically insulating material, has a topsurface and a bottom surface opposite to the top surface, and is formedwith a plurality of spaced-apart through holes. Each of the throughholes is defined by an interior wall surface and penetrates the top andbottom surfaces.

Each of the layered active metal parts is formed at least upon arespective one of the interior wall surfaces.

The layered electrodes are respectively formed on the layered activemetal parts.

The reaction confinement layer is disposed on the substrate and confinesa reactor space over a region of the substrate where the through holesare formed.

The electrochemical reactive layer is disposed in the reactor space andis electrically coupled to the layered electrodes.

The cover piece is disposed to cover the electrochemical reactive layer.

According to another aspect of the present invention, an electrochemicalbiosensor may be adapted for use with a measuring device and include asubstrate, an electrochemical reactive layer, a plurality ofelectrically-conductive vias and a cover piece.

The substrate is made of an electrically insulating material, has a topsurface and a bottom surface opposite to the top surface, and is formedwith a plurality of spaced-apart through holes. Each of the throughholes is defined by an interior wall surface and penetrates the top andbottom surfaces.

The electrochemical reactive layer is disposed on the substrate.

Each of the electrically-conductive vias is formed at least inside arespective one of the interior wall surfaces and has a bottom part thatis proximal to the bottom surface of the substrate and that isconfigured to have electrical contact with a corresponding portion ofthe measuring device, and a top part that is proximal to the top surfaceof the substrate and that is electrically coupled to the electrochemicalreactive layer.

The cover piece is disposed to cover the electrochemical reactive layer.

According to yet another aspect of the present invention, a method forproducing an electrochemical biosensor may include: forming a pluralityof spaced-apart through holes in an electrically insulating substrate,the through holes penetrating top and bottom surfaces of theelectrically insulating substrate; forming a plurality of layered activemetal parts respectively in the through holes; forming a plurality oflayered electrodes respectively on the layered active metal parts; andforming an electrochemical reactive layer on one of the top and bottomsurfaces of the substrate to electrically connect the layeredelectrodes.

According to a further aspect of the present invention, a method forproducing an electrode of an electrochemical biosensor may include stepsof: forming a through hole in an electrically insulating substrate;activating at least a portion of an interior wall surface within thethrough hole; and forming a layer of metal-containing electrode materialon the portion of the interior wall surface to produce the electrode.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the present invention will becomeapparent in the following detailed description of the exemplaryembodiments with reference to the accompanying drawings, of which:

FIG. 1 is an exploded perspective view, illustrating an electrochemicalbiosensor;

FIG. 2 is an exploded perspective view, illustrating anotherelectrochemical biosensor;

FIG. 3 is a partly exploded perspective view, illustrating oneembodiment of an electrochemical biosensor;

FIG. 4 is a perspective view of one embodiment;

FIG. 5 is a fragmentary sectional view taken along line V-V in FIG. 4;

FIG. 6 is a fragmentary sectional view, illustrating a layered electrodeformed in and beyond a through hole;

FIG. 7 is a fragmentary sectional view of one embodiment, illustratingthe electrochemical biosensor;

FIG. 8 is a fragmentary sectional view of one embodiment, illustratinganother configuration of the layered electrode;

FIG. 9 is a schematic flow diagram of forming the layered electrode ofthe electrochemical biosensor of one embodiment; and

FIG. 10 is a flow chart illustrating a method for producing theelectrochemical biosensor of one embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Before the present invention is described in greater detail, it shouldbe noted that like elements are denoted by the same reference numeralsthroughout the disclosure.

Referring to FIGS. 3 to 6, a first exemplary embodiment of anelectrochemical biosensor 1 according to the present invention is shownto include a substrate 2, a plurality of layered active metal parts 3, aplurality of layered electrodes 4, a reaction confinement layer 5, anelectrochemical reactive layer 6, and a cover piece 7.

The substrate 2, which has a top surface 21 and a bottom surface 22opposite to the top surface 21, is formed with a plurality ofspaced-apart through holes 231. Each of the through holes 231 is definedby an interior wall surface 23 and penetrates the top and bottomsurfaces 21, 22. In this embodiment, the substrate 2 is made of anelectrically insulating material and is configured in a rectangularshape. Examples of the electrically insulating material may include, butare not limited to, polyethylene (PE), polyimide (PI) and polycarbonate(PC). In this embodiment, the number of the through holes 231 formed inthe substrate 2 is two, but the number of the through holes 231according to the present invention is not limited to what is disclosedin this embodiment.

As shown in FIG. 5, in this embodiment, the top surface 21 of thesubstrate 2 has a plurality of top to-be-plated zones 211 thatrespectively extend around the through holes 231, and a plurality of topseparating zones 212 that extend respectively around the topto-be-plated zones 211 and that respectively isolate the topto-be-plated zones 211 from a top plating-free zone 213 of the topsurface 21. Similarly, the bottom surface 22 of the substrate 2 has aplurality of bottom to-be-plated zones 221 that respectively extendaround the through holes 231, and a plurality of bottom separating zones222 that extend respectively around the bottom to-be-plated zones 221and that respectively isolate the bottom to-be-plated zones 221 from abottom plating-free zone 223 of the bottom surface 22. In thisembodiment, the top and bottom to-be-plated zones 211, 221, and theinterior wall surfaces 23 are roughened, but it should be noted that, inother embodiments, the top and bottom to-be-plated zones 211, 221,and/or the interior wall surfaces 23 may be partially roughened or notroughened at all.

As shown in FIG. 6, each of the layered active metal parts 3 is formedat least upon a respective one of the interior wall surfaces 23 of thesubstrate 2 and corresponds in position to a respective one of thethrough holes 231. In this embodiment, each of the layered active metalparts 3 extend outwardly from the respective one of the interior wallsurfaces 231 to cover the top and bottom to-be-plated zones 211, 221which surround the respective one of the interior wall surfaces 231. Insome embodiments, the layered active metal parts 3 may be made of amaterial that is selected from the group consisting of palladium,rhodium, platinum, iridium, osmium, gold, nickel and combinationsthereof.

Referring to FIGS. 5 and 6, the layered electrodes 4 are made of ametal-containing electrode material and are respectively formed on thelayered active metal parts 3, which correspond respectively in positionto the through holes 231. In this embodiment, each of the layeredelectrodes 4 includes a first layered metal part 41 bonded to therespective one of the layered active metal parts 3, and a second layeredmetal part 42 bonded to the first layered metal part 41 and opposite tothe respective one of the layered active metal parts 3. In someembodiments, the first layered metal parts 41 of the layered electrodes4 may be made of a material selected from the group consisting ofcopper, nickel, silver and combinations thereof. In some embodiments,the second layered metal parts 42 of the layered electrodes 4 may bemade of a material selected from the group consisting of gold, nickel,titanium and combinations thereof. In such embodiments, gold is morepreferred owing to its relatively high affinity to biological reagents.It should be noted that, in some embodiments, the layered electrodes 4may be single-layered, for instance, and have only the first layeredmetal parts 41. In some other embodiments, each of the layeredelectrodes 4 may be configured in a multilayered structure having aplurality of stacking layers made of identical material by similarprocesses. In this embodiment, as shown in FIG. 6, each of the layeredelectrodes 4 partially fills the respective one of the through holes 231and has an annular cross-section inside the respective one of thethrough holes 231. However, the through holes 231 may be completelyfilled up by the layered electrodes 4 in other embodiments in accordancewith the present invention.

Referring to FIGS. 3 to 5, the reaction confinement layer 5 is disposedon the top surface 21 of the substrate 2 and is formed with a reactorspace 51 over a region of the substrate 2 where the through holes 231are formed. In this embodiment, the reaction confinement layer 5 isconfigured in a rectangular shape and has a bottom surface that isadhered to the top surface 21 of the substrate 2. As shown in FIG. 4, awidth of the reaction confinement layer 5 is substantially identical tothat of the substrate 2. It should be noted that, in some embodiments,the substrate 2 and the reaction confinement layer 5 may be integrallyformed as one piece. As shown in FIG. 3, in this embodiment, the reactorspace 51 is configured as a rectangular notch formed at a longitudinalside of the reaction confinement layer 5 to confine the electrochemicalreactive layer 6 therein.

As shown in FIG. 5, the electrochemical reactive layer 6 is disposed inthe reactor space 51 to cover the layered electrodes 4 and iselectrically coupled to the layered electrodes 4. The electrochemicalreactive layer 6 may be electrochemically reactive with an analyte in asample liquid (not shown) introduced into the reactor space 51, so as togenerate an output electrical signal that may be transmitted to thelayered electrodes 4, to which a coupling portion of an externalmeasuring device may be coupled for reading the output electricalsignal.

The cover piece 7 is disposed to cover the electrochemical reactivelayer 6. In this embodiment, a bottom surface of the cover piece 7 isadhered to a top surface of the reaction confinement layer 5. In thisembodiment, the cover piece 7 is configured in a rectangular shape andhas a length and a width substantially identical to those of thereaction confinement layer 5. The reactor space 51 of the reactionconfinement layer 5 is further confined by the substrate 2, theelectrochemical reactive layer 6 and the cover piece 7 to form asample-receiving space 72 for receiving the sample liquid. In addition,the substrate 2, the reaction confinement layer 5, and the cover piece 7may cooperatively define a sample inlet 71 at the longitudinal side ofthe substrate 2 for introduction of the sample liquid into thesample-receiving space 72.

By forming the layered active metal parts 3 on the interior wallsurfaces 231 and on the top and bottom to-be-plated zones 211, 221, thelayered electrodes 4, which are respectively formed on the layeredactive metal parts 3, can be tightly and firmly bonded to the substrate2 via the layered active metal parts 3. Moreover, the layered activemetal parts 3 and the layered electrodes 4 constitute a plurality ofelectrically conductive vias each of which is at least formed along andinside a respective one of the through holes 231. Each of theelectrically conductive vias has a top part that is proximal to the topsurface 21 and that is electrically coupled to the electrochemicalreactive layer 5, and a bottom part that is proximal to the bottomsurface 22 of the substrate 2 and that is configured to have electricalcontact with the coupling portion of the external measuring device (notshown), so that the electrical output signal resulting from theelectrochemical reaction between the analyte and the electrochemicalreactive layer 6 can be transmitted through the electrically conductivevias to the coupling portion of the external measuring device. As such,a process for assembling electrodes to the substrate can thereby beomitted, so as to simplify the manufacturing process of theelectrochemical biosensor 1 and to enhance production efficiencythereof.

Referring to FIG. 7, a second exemplary embodiment of theelectrochemical biosensor according to the present invention is shown tobe similar to that of the first embodiment with the differencetherebetween residing in that, in the second exemplary embodiment, thelayered active metal parts 3′ (only one is shown) and the layeredelectrodes 4′ (only one is shown) are merely formed on the interior wallsurfaces 23′ (only one is shown), respectively, and are limited fromextending therebeyond. That is to say, the electrically-conductive vias,which are composed of the layered active metal parts 3′ and the layeredelectrodes 4′, are disposed respectively inside the through holes 231′(only one is shown) and are flush with the top and bottom surfaces 21′,22′ of the substrate 2′. In this embodiment, the coupling portion of theexternal measuring device can be configured to have protrusions forenhancement of electrical contact with the electrically-conductive vias.

Referring to FIG. 8, a third exemplary embodiment of the electrochemicalbiosensor is shown to be similar to the second exemplary embodiment. Thedifference between the second and third exemplary embodiments resides inthat each layered active metal parts 3″ in the third exemplaryembodiment is limited from extending beyond the respective one of theinterior wall surfaces 23″ and is not flush with the bottom surface 22″of the substrate 2″. It should be noted that, in other embodiments, thelayered active metal parts 3″ (only one is shown) may be limited fromextending beyond the interior wall surfaces 23″ (only one is shown) andbe not flush with the top surface 21″ (or be not flush with both the topand bottom surfaces 21″,22″). Similar to the second exemplaryembodiment, the coupling portion of the external measuring device may beconfigured to have protrusions for enhancement of electrical contactwith the electrically-conductive vias.

Referring to FIGS. 9 and 10, a method for producing the electrochemicalbiosensor of the first exemplary embodiment according to the presentinvention includes steps as follows.

Step 101: forming a plurality of the spaced-apart through holes 231 inthe electrically insulating substrate 2. Note that for the sake ofsimplicity, only one through hole 231 and components/parts associatedwith said one through hole 231 are depicted in FIG. 9. The through holes231 penetrate top and bottom surfaces 21, 22 of the substrate 2. In thisembodiment, the forming of the through holes 231 is conducted usinglaser. However, in other embodiments, the forming of the through holes231 may be conducted using other techniques, such as mechanicalpunching.

Step 102: forming a plurality of the layered metal parts 3 in thethrough holes 231 and on peripheral surface areas of the top and bottomsurfaces 21, 22 which respective extend around the through holes 231.The top and bottom to-be-plated zones 211, 221 are respectively locatedon the peripheral surface areas of the top and bottom surfaces 21, 22and have the layered active metal parts 3 formed thereon. In thisembodiment, the forming of the layered active metal parts 3 includesroughening the interior wall surfaces 23 and the top and bottomto-be-plated zones 211, 221, followed by immersing the substrate 2 intoan active metal solution. In this embodiment, the active metal solutionis a Palladium—Tin colloid solution and has a palladium concentrationranging from 1 ppm to 750 ppm. Since the interior wall surfaces 23 andthe top and bottom to-be-plated zones 211, 221 are roughened, thelayered active metal parts 3 formed on the top and bottom to-be-platedzones 211, 221 may be thicker than active metal layers formed on otherportions of the peripheral surface areas of the top and bottom surfaces21, 22 (see FIG. 9). As mentioned hereinbefore, the interior wallsurfaces 23 and the top and bottom to-be-plated zones 211, 221 may bepartially roughened or not roughened at all in other embodimentsaccording to the present invention.

Step 103: forming a plurality of the layered electrodes 4 respectivelyon the layered active metal parts 3. In this embodiment, the forming ofthe layered electrodes 4 includes forming a plurality of the firstlayered metal parts 41 respectively on the layered active metal parts 3,removing a portion of each of the layered active metal parts 3 and eachof the first layered metal parts 41 from a respective one of theperipheral surface areas, and forming a plurality of second layeredmetal parts 42 respectively on the first layered metal parts 41remaining on the top and bottom to-be-plated zones 211, 221.

The forming of the first layered metal parts 41 may be conducted byelctroless plating. In this embodiment, the forming of the first layeredmetal parts 41 is conducted by immersing the substrate 2 into anelectroless-plating cooper solution at a temperature ranging from 50° C.to 55° C. for 2 to 5 minutes.

The partial removal of the first layered metal parts 41 and the activemetal parts 3 is conducted by laser etching, so that the top and bottomto-be-plated zones 211, 221 are isolated respectively by the top andbottom separating zones 212, 222 from the top and bottom plating-freezones 213, 223, respectively, and so that the top and bottom separatingzones 212, 222 are free of the layered active metal parts 3 and thefirst layered metal parts 41. In this embodiment, the laser power rangesfrom 5 to 10 watts with a pulse frequency ranging from 20 to 50 kHz.

In this embodiment, the forming of the second layered metal parts 42 isconducted by electroplating. By virtue of the top and bottom separatingzones 212, 222, the second layered metal parts 42 may be merely formedon the layered active metal parts 3 which are formed on the top andbottom to-be-plated zones 211, 221 and on the interior wall surfaces 23.

After the forming of the second layered metal parts 42, those of thelayered active metal parts 3 and the first layered metal parts 41, whichare formed on the top and bottom plating-free zones 213, 223 are removedusing, for example, chemical etching techniques.

Step 104: disposing the reaction confinement layer 5 onto the topsurface 21 of the substrate 2 to confine the reactor space 51 over theregion of the substrate 2, where the through holes 231 and the layeredelectrodes 4 are formed (see FIG. 3). In this embodiment, the reactorspace 51 has an open end that is flush with a longitudinal side of thesubstrate 2. It should be noted that in other embodiments, the reactionconfinement layer 5 and the substrate 2 may be integrally formed as onepiece.

Step 105: forming the electrochemical reactive layer 6 on the topsurface 21 of the substrate 2 and in the reactor space 51 toelectrically connect the layered electrodes 4 (see FIG. 3). In thisembodiment, the forming of the electrochemical reactive layer 6 isconducted by distributing a layer of electrochemical reagents onto thetop surface 21 of the substrate 2 in the reactor space 51 to cover thelayered electrodes 4.

Step 106: attaching the cover piece 7 onto the reaction confinementlayer 5 to cover the electrochemical reactive layer 6 and the layeredelectrodes 4 (see FIG. 3).

It is worth noting that, in some embodiments, the forming of the layeredactive metal parts 3 may be conducted by screen printing. In suchembodiments, the screen printing includes applying an active metalsolution onto the top and bottom to-be-plated zones 211, 221 andallowing the active metal solution to flow into the through holes 231,thereby forming the layered active metal parts 3 only on the top andbottom to-be-plated zones 211, 221 and on the interior wall surfaces 23.Thus, no top and bottom separating zones 212, 222 are needed in suchembodiments in accordance with the present invention.

In addition, instead of the screen printing, the layered active metalparts 3 may be formed using laser direct structuring techniques(developed by LPKF Laser& Electronics, AG), i.e., using laser toactivate a layer of metal-ion-containing plastic material formed on theinterior wall surfaces 23 and the top and bottom to-be-plated zones 211,221.

A method for producing the layered electrode of the electrochemicalbiosensor of the second exemplary embodiment according to the presentinvention is similar to that of the first exemplary embodiment andincludes the following steps of, referring to FIG. 7,: forming aplurality of the spaced-apart through holes 231′ on the insulatingsubstrate 2′; forming a plurality of the layered active metal parts 3′respectively on the interior wall surfaces 23′ which respectively definethe through holes 231′; and forming a plurality of the layeredelectrodes 4′ respectively on the layered active metal parts 3′. Theforming of the layered active metal parts 3′ includes roughening theinterior wall surfaces 23′ by laser, and immersing the substrate 2′ intoan active metal solution to form the layered active metal parts 3′. Theforming of the layered electrodes 4′ includes forming a plurality of thefirst layered metal parts 41′ onto the layered active metal parts 3′ byelectroless plating, removing the first layered metal parts 41′ and thelayered active metal parts 3′ on the top and bottom surfaces 21′, 22′,and forming a plurality of second layered metal parts 42′ onto theremaining first layered metal parts 41′ (i.e., those on the interiorwall surfaces 23′) by electroplating, so as to obtain the layeredelectrodes 4′.

To sum up, by virtue of the electrically-conductive vias, the electricaloutput signal resulting from the electrochemical reaction between theanalyte in the sample liquid and the electrochemical reactive layer 6can be transmitted to the coupling portion of the external measuringdevice. As such, the production cost for the electrochemical biosensorof the present invention can be effectively lowered, and attenuation andinterference of the electrical output signal can also be reduced.Moreover, the method for producing the electrochemical biosensoraccording to the present invention may assure relatively stable bondingbetween the layered electrodes 4/4′/4″ and the substrate 2/2′/2″, aswell as to achieve a relatively simple manufacturing process.

While the present invention has been described in connection with whatare considered the most practical and preferred embodiments, it isunderstood that this invention is not limited to the disclosedembodiments but is intended to cover various arrangements includedwithin the spirit and scope of the broadest interpretation so as toencompass all such modifications and equivalent arrangements.

What is claimed is:
 1. A method for producing an electrochemicalbiosensor, comprising the steps of: forming a plurality of spaced-apartthrough holes in an insulating substrate, the through holes penetratingtop and bottom surfaces of the insulating substrate; forming a pluralityof layered active metal parts respectively in the through holes; forminga plurality of layered electrodes respectively on the layered activemetal parts, each of the layered electrodes extending into a respectiveone of the through holes along the respective one of the layered activemetal parts; disposing a reaction confinement layer onto the top surfaceof the substrate to confine a reactor space surrounding the throughholes; forming an electrochemical reactive layer on the top surface ofthe substrate and in the reactor space to electrically connect thelayered electrodes; and attaching a cover piece onto the reactionconfinement layer to cover the electrochemical reactive layer and thelayered electrodes, in such a manner that the reactor space is furtherconfined by the substrate, the electrochemical reactive layer and thecover piece to form a sample-receiving space, and that the substrate,the reaction confinement layer and the cover piece cooperatively definea sample inlet that is located at a side of the substrate and that is inspatial communication with the sample-receiving space for introductionof a sample liquid into the sample-receiving space.
 2. The method ofclaim 1, wherein during the forming of the layered active metal parts,each of the layered active metal parts formed inside the respective oneof the through holes is flush with at least one of the top and bottomsurfaces of the substrate.
 3. The method of claim 1, wherein during theforming of the layered active metal parts, each of the layered activemetal parts is limited from extending beyond the respective one of thethrough holes and is not flush with at least one of the top and bottomsurfaces of the substrate.
 4. The method of claim 1, wherein during theforming of the layered active metal parts, each of the layered activemetal parts extends outwardly from a respective one of the through holesand covers a peripheral surface area of at least one of the top andbottom surfaces of the substrate, which extends around the respectiveone of the through holes.
 5. The method of claim 4, wherein the formingof the layered active metal parts is conducted by screen printing. 6.The method of claim 5, wherein the screen printing includes applying anactive metal solution onto the peripheral surface areas of the at leastone of the top and bottom surfaces and allowing the active metalsolution to flow into the through holes.
 7. The method of claim 1,wherein the forming of the layered active metal parts includesroughening interior wall surfaces of the substrate within the throughholes.
 8. The method of claim 7, wherein the forming of the layeredactive metal parts further includes immersing the substrate into anactive metal solution after roughening the interior wall surfaces of thesubstrate within the through holes.
 9. The method of claim 1, whereinthe forming of the layered electrodes includes forming a plurality offirst layered metal parts respectively onto the layered active metalparts by electroless plating, and forming a plurality of second layeredmetal parts respectively on the first layered metal parts byelectroplating, such that each of the first layered metal parts togetherwith a respective one of the second layered metal parts constitutes oneof the layered electrodes.
 10. The method of claim 4, wherein theforming of the layered electrodes includes: forming a plurality of firstlayered metal parts respectively on the layered active metal parts thatare on the at least one of the top and bottom surfaces by electrolessplating; and removing partially each of the layered active metal partsand each of the first layered metal parts from a respective one of theperipheral surface areas, so that a separating zone of the respectiveone of the peripheral surface areas is free of the layered active metalpart and the first layered metal part, and that a to-be-plated zoneextends around a respective one of the through holes and has the layeredactive metal part and the first layered metal part remained thereon. 11.The method of claim 3, wherein the forming of the layered active metalparts includes forming the layered active metal parts respectivelywithin the through holes and on the at least one of the top and bottomsurfaces of the substrate; and wherein the forming of the layeredelectrodes includes: forming a plurality of first layered metal partsrespectively on the layered active metal parts by electroless plating;and removing a portion of each of the layered active metal partstogether with a portion of a respective one of the first layered metalparts, which is formed on the at least one of the top and bottomsurfaces of the substrate.
 12. The method of claim 1, wherein thereaction confinement layer extends to the side of the substrate.